1. Field of the Invention
This invention relates to a printing machine for making a printing plate by recording and developing an image on the plate, and thereafter printing the image by feeding ink to the plate.
2. Description of the Related Art
In an ordinary conventional printing machine, a prepress process is carried out first to make a printing plate by exposing the plate placed in contact with a film having a binary black and white image recorded thereon. Then, the plate is loaded into a printing apparatus to carry out a printing process.
Recently, printing machines commonly called digital printers have been proposed, one such printer being capable of performing both the prepress process and printing process. A digital printer, as described in U.S. Pat. No. 6,050,188, for example, employs a “computer-to-plate” system for forming an image on a printing plate by directly scanning and exposing the plate with laser beams or the like modulated with image signals.
A printing machine as described in U.S. Pat. No. 6,050,188 has, arranged in the same space, plate cylinders for holding printing plates mounted peripherally thereof, blanket cylinders with blankets mounted peripherally thereof, an impression cylinder, image recorders for recording images on the printing plates mounted peripherally of the plate cylinders, and ink feeders for feeding inks to the printing plates mounted peripherally of the plate cylinders. A recording head is disposed close to each plate cylinder for recording images on the printing plate mounted peripherally of the plate cylinder.
In the printing machine capable of performing both the prepress process and printing process described above, the recording head is disposed around each plate cylinder even at a printing time. Mists and particles of the inks, water, paper and so on floating in the printing machine tend to adhere to the recording head, The quantity of light for recording could thereby be reduced to record defective images. This results in the inconvenience of having to clean the recording head periodically.